Biology subjects

Patra, S.

Publications and source records attributed to Patra, S..

18 recordsLinked to original sources

bioRxiv2026

Individual mouse mitotic chromosomes exhibit cell type-specific differences in biomechanical properties

Cyclic episodes of chromosome compaction and de-condensation are features of eukaryotic cell division that aid mitotic segregation and help prevent aneuploidy. While biophysical data on mitotic chromosome structure has been previously obtained, heterogeneity within samples can confound analyses and precludes direct like-for-like comparisons. To circumvent this, we employed advanced flow cytometry to purify specific metaphase chromosomes with biotinylated telomeres from stably engineered mouse cells. We show that ESC-derived metaphase chromosomes 3 and 19 display distinct properties but share a conserved force-dependent mechanical response. In contrast, chromosome equivalents isolated from NSCs and preB cells show markedly different force-dependent responses, reflecting progressive differentiation stages. Covalent crosslinking of ESC-derived chromosomes alters biomechanical properties to mimic equivalents from more differentiated cells. Collectively, these results highlight the need to isolate specific, homogeneous metaphase chromosome samples to accurately decipher their complex behaviours.

biophysics↗

bioRxiv2026

Quantifying the binding affinity of a pharmacological chaperone to transient unfolded states of a normally folded protein

Binding of ligands to partially or fully unfolded proteins can play a key role in the mechanism of cellular and pharmacological chaperones, facilitating proper folding. However, it is challenging to quantify the binding affinity of ligands for unfolded states in a protein that is normally folded, as the methods standardly used to destabilize the native fold also affect ligand binding. We used single-molecule force spectroscopy to unfold single protein molecules without altering solution condi-tions and observe interactions of a ligand with unfolded states. Focusing on pentosan polysulfate (PPS), an anti-prion pharmacological chaperone previously shown to interact with both the native and partially or fully unfolded states of the prion protein, we measured the concentration-dependent effects of PPS binding on the conformational dynamics of bank vole prion protein (BvPrP) molecules held in optical tweezers. We found that PPS stabilized certain partially unfolded intermediate states of BvPrP as well as the fully unfolded state. Strikingly, the tendency to bind unfolded states instead of the folded state increased as the PPS concentration was reduced, implying a higher affinity to unfolded states. From the relative amount of binding to unfolded versus folded states, we estimated that PPS bound roughly 100-fold more tightly to unfolded states than to the native state of PrP. These results reinforce the likely importance of unfolded states in prion misfolding and propagation. More generally, they show how binding affinity to transient, unstable states can be estimated.

biophysics↗

bioRxiv2026

IRES-mediated translation of delta160p53 regulates p53 functions and fine-tunes cancer homeostasis

Mutations in p53 and its 12 isoforms can alter its functions. As N-terminally truncated isoforms of p53 (delta40p53, delta133p53, and delta160p53) participate in tetramer formation, they are important regulators of cancer fate. Although delta40p53- and delta133p53-mediated regulation of cancer is well reported, the mechanism underlying delta160p53 production and its functional role remains unclear. We investigated the internal ribosomal entry site (IRES)-mediated translation of {Delta}160p53 and its role in cancer regulation. As differential synthesis of delta160p53 was observed under different stress conditions, IRES-mediated translation of this isoform was demonstrated using bicistronic luciferase constructs. No cryptic promoters or splicing sites were detected in the IRES sequence. Cell death and late apoptosis were significantly decreased, while proliferation, the number of cells in the S phase, and drug resistance were induced by delta160p53. Furthermore, delta160p53 did not induce p53-responsive promoters. RNA sequencing analysis of delta160p53 overexpression showed similar results, along with the inhibition of other tumor suppressor genes. Overall, our results provide insights into IRES-mediated translation of delta160p53, which can be considered a novel target for cancer treatment.

molecular biology↗

bioRxiv2026

Evolutionary genomics of host-transposon conflict, multilevel selection, and Red Queen dynamics

Transposable elements (TE) jump from one genomic locus to another. Since increase in their copy number is a metabolic burden for the host, TE are considered as genomic parasites. Although host-TE co-existence is regarded as an evolutionary arms race, the hypothesis is not extensively tested especially using evolutionary genomics. We provide a hypothesis testing framework to understand the distribution of TE in genic regions of the host genome, variation in the regulation of TE by host, and effect of these two factors on host-TE co-evolutionary dynamics. We test our hypothesis by understanding the distributions of potentially active TEs in the genome of 78 teleost fishes, representing major families and orders within the clade. Our analysis reveals coevolutionary arms race predicted by the Red Queen dynamics.

evolutionary biology↗

bioRxiv2026

Target DNA-Mediated Plasmonic Coupling and Assembly Kinetics of Gold Nanorods for Label-Free Nucleic Acid Detection

DNA-programmed assembly of plasmonic nanostructures provides a powerful route to couple molecular recognition with optical signal generation. Here, we report the sequence-specific assembly of DNA-functionalized gold nanorods using a sesame allergen-derived DNA biomarker as a molecular bridge. Target-induced assembly produces concentration-dependent assembly growth, plasmon coupling, and distinct assembly kinetics that are readily monitored by absorption spectroscopy, enabling label-free detection of the target DNA in the nanomolar concentration range. The assembled nanorods further produce strong surface-enhanced Raman scattering (SERS) signals arising from plasmonic coupling within the assemblies, extending detection to the picomolar regime without the use of Raman reporters. Quantitative analysis reveals that both the extent and rate of assembly formation are governed by target DNA concentration. These results establish a direct relationship between molecular recognition, assembly growth, plasmonic coupling, and spectroscopic response, highlighting DNA-programmed gold nanorod assembly as a versatile platform for investigating hybridization-driven plasmonic self-assembly and nucleic acid detection. Table of Content O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/732610v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@e4fcb9org.highwire.dtl.DTLVardef@18c0d89org.highwire.dtl.DTLVardef@1ccb4bborg.highwire.dtl.DTLVardef@6d84ca_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2026

Putative G-Quadruplex Structures in Cancer-Dysregulated Circulating lncRNAs and their G4-mediated Identification of Protein Interacting Partners

Circulating long non-coding RNAs (lncRNAs) have emerged as compelling cancer biomarkers. However, the structural features that mediate their extracellular stability and protein interactions remain largely unexplored. Here, we present the first systematic investigation of G-quadruplex (G4) motifs within cancer-dysregulated circulating lncRNAs and exploit these structures as molecular handles to identify associated RNA-binding protein (RBP) networks. From 283 circulating lncRNAs curated from the Lnc2Cancer 3.0 database, putative G-quadruplex-forming sequences (PQSs) were identified computationally using QGRS Mapper and G4Hunter, yielding four prioritized candidates -- AGAP2-AS1, LINC00683, DLG1-AS1, and KRTAP5-AS1 -- spanning 2G to 4G architectures. In vitro transcribed PQSs were validated for parallel G4 formation by circular dichroism spectroscopy, native polyacrylamide gel electrophoresis with thioflavin T staining, and reverse transcriptase stop assays, conducted under both standard buffer and simulated body fluid conditions to approximate the circulatory milieu. Electrophoretic mobility shift assays and isothermal titration calorimetry demonstrated nanomolar-affinity interactions between the G4-containing RNA and human serum albumin (HSA), the most abundant circulating protein. Cross-referencing G4-interacting proteins from the G4IPDB database with lncRNA-protein associations from LncTarD and NPInter, combined with RPISeq interaction predictions, identified ten candidate RBPs. A STRING-based protein-protein interaction (PPI) network was constructed at a confidence threshold of [≥]0.7 and refined iteratively using experimental stability data to exclude proteins associated exclusively with the structurally weaker KRTAP5-AS1. The resulting network, centered on ELAVL1, IGF2BP1, hnRNPA2B1, and FUS, highlights a coordinated post-transcriptional regulatory module relevant to oncogenesis. This work establishes a novel, experimentally validated framework wherein G4 motifs serve as entry points for decoding the protein interactome of circulating lncRNAs, with implications for cancer diagnostics and RNA-targeted therapeutic strategies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=64 SRC="FIGDIR/small/728349v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1bba7dborg.highwire.dtl.DTLVardef@1095a53org.highwire.dtl.DTLVardef@1092eddorg.highwire.dtl.DTLVardef@1e3b7e7_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2026

Mechanistic Insights into TMPyP4 Recognition of the HIV-1 LTR-III G-Quadruplex in Dilute and Protein Condensate Environments Reveal Hidden Dual Binding Modes

G-quadruplex (GQ) structures within the HIV-1 long terminal repeat (LTR) regulate viral transcription and represent promising antiviral targets; however, detailed mechanistic understanding of their ligand recognition at the molecular level remains limited and has largely been investigated under dilute conditions despite the crowded and compartmentalized nature of intracellular environment. Here, we investigate the interaction of the cationic porphyrin TMPyP4 with the HIV-1 LTR-III GQ under dilute conditions and inside protein-rich phase-separated condensates that mimic intracellular biocondensates. Steady-state and time-resolved fluorescence measurements reveal a dual binding behavior that is not discernible from absorption spectroscopy. A high-affinity guanine-rich binding mode leads to efficient fluorescence quenching through electron transfer from ground-state guanine to excited TMPyP4, whereas a weaker non-guanine binding mode gives rise to enhanced and long-lived emission. Nucleotide-specific control experiments validate the origin of these distinct binding environments. Molecular docking and molecular dynamics simulations further support preferential binding of TMPyP4 at the terminal G-quartet together with a secondary binding mode near the quadruplex-duplex junction. Importantly, both TMPyP4 and LTR-III GQ preferentially partition into the condensates, where the hybrid GQ structure, dual binding behavior, and associated excited-state signatures remain preserved despite the crowded and viscous environment. Although a slight reduction in binding affinity is observed inside the condensates, the overall binding mechanism remains largely preserved due to compensatory effects arising from the condensate microenvironment. Overall, this work demonstrates that ligand recognition of viral GQ remains preserved within protein condensates and establishes fluorescence spectroscopy as a sensitive approach for resolving hidden binding heterogeneity in GQ-ligand interactions.

biophysics↗

bioRxiv2025

Structural insights into DNA annealing and recombination by herpesviral DNA-binding proteins ICP8 and BALF2

The DNA-binding proteins of herpesviruses are key factors involved in multiple stages of DNA replication and recombination. The well-studied ICP8 protein of Herpes Simplex Virus 1 binds single-stranded DNA in a cooperative manner and facilitates the annealing of complementary DNA strands in a process that involves the formation of double helical filaments. Moreover, it cooperates with UL12 alkaline nuclease to execute recombination between homologous DNA sequences. In this work, we present the structures of ICP8 and its homolog BALF2 of the Epstein-Barr Virus in complexes with DNA. These structures reveal a conserved conformation of the bound DNA in which several bases are rotated away from the protein, enabling homology search and base-pairing. The crystal structures of ICP8-DNA depict the pairing between two DNA strands, showing the flexibility of base-pairing. In the structure of the double filament of ICP8, we visualize the interactions between protein subunits within and between the antiparallel strands. Finally, we present the first complete structure of a ternary recombinase complex composed of ICP8 and UL12 bound to a model DNA. This structural landscape illustrates the different stages of the DNA recombination process in herpesviruses, shedding light on molecular mechanisms of their replication.

molecular biology↗

bioRxiv2024

Complete Genome Sequence, Metabolic Profiling and Functional Studies reveal Ligilactobacillus salivarius LS-ARS2 is a Promising Biofilm-forming Probiotic with Significant Antioxidant, Antibacterial, and Antibiofilm Potential

BACKGROUNDProbiotics restore microbial balance and prevent gut-inflammation. Therefore, finding out novel probiotic strains is a demand. As gut-microbe, benefits of Ligilactobacillus salivarius (LS) are established. However, strain-specific detailed studies are limited. Here, we illustrate probiotic attributes of novel LS-ARS2 for its potential application as food-supplement and/or therapeutic to improve gut-health. METHODSWhole genome sequencing (WGS) and phylogenetic analysis confirm the strain as LS. To establish probiotic properties, acid-bile tolerance, auto-aggregation, cell-surface-hydrophobicity, biofilm-formation and adhesion-assays are performed. To ensure safety attributes, antibiotic-susceptibility, haemolytic, DNase, trypan-blue and MTT assays are done. ABTS, DPPH, superoxide, hydroxyl free radical scavenging assays are used to determine anti-oxidant potential. Antibacterial assays including co-culture assay with pathogen and pathogenic biofilm-inhibition assays are performed to explore antibacterial efficacy. To characterize metabolic-profile of LS-ARS2-derived cell-free-supernatant (CFS), HRMS analysis are carried out. Consequently, WGS-analyses predict potential molecular associations related to functional outcomes. RESULTSWe find LS-ARS2 as remarkable fast-growing strain that shows acid and bile tolerance (>60% survival rate) indicating promising gut-sustainability. High auto-aggregation capacity (>80%), robust cell-surface hydrophobicity (>85%), and adhesion efficacy to Caco-2 cells illustrate significant potential of LS-ARS2 for gut colonization. Fascinatingly, LS-ARS2 is able to form biofilm within 24 h (p<0.0001), rare among LS strains, indicating the potential of the strain for efficient stay in the gut. The strain ensures safety attributes. LS-ARS2-WGS analysis recognizes probiotic-specific determinants, predicts genomic stability, identifies orthologous-clusters for diverse functions, and predicts metabolites and bacteriocins. HRMS-studies with LS-ARS2-CFS further validate the presence of diverse beneficial metabolites with antimicrobial and immunomodulatory potential. LS-ARS2 shows significant antioxidant properties in ABTS (>60%), DPPH (>10U/mL), superoxide (>70%), and hydroxyl free radical scavenging assays (>70%). Further, LS-ARS2 shows antimicrobial activities against Gram-positive Methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative multidrug-resistant clinical strains enterotoxigenic Escherichia coli, Vibrio cholerae, and Shigella flexneri. Anti-Salmonella effect of LS-ARS2 is prominent (p<0.0001). Most interestingly, LS-ARS2-CFS inhibits MRSA-biofilm (p<0.0001), again rare among LS strains. CONCLUSIONS LS-ARS2 is a novel fast-growing, biofilm-forming probiotic with significant antioxidant, antibacterial, and anti-biofilm potentials, suggesting the promising applications of LS-ARS2 for combating pathogenic biofilms and improving gut-health. However, further in vivo studies would facilitate their potential applications.

microbiology↗

bioRxiv2024

Gene mobility elements mediate cell type specific genome organization and radial gene movement in vivo

ABSTRACTUnderstanding the level of genome organization that governs gene regulation remains a challenge despite advancements in chromatin profiling techniques. Cell type specific chromatin architectures may be obscured by averaging heterogeneous cell populations. Here we took a reductionist perspective, starting with the relocation of the hunchback gene to the nuclear lamina in Drosophila neuroblasts. We previously found that this event terminates competence to produce early-born neurons and is mediated by an intronic 250 base-pair element, which we term gene mobility element (GME). Here we found over 800 putative GMEs globally that are chromatin accessible and are Polycomb (PcG) target sites. GMEs appear to be distinct from PcG response elements, however, which are largely chromatin inaccessible in neuroblasts. Performing in situ Hi-C of purified neuroblasts, we found that GMEs form megabase-scale chromatin interactions, spanning multiple topologically associated domain borders, preferentially contacting other GMEs. These interactions are cell type and stage-specific. Notably, GMEs undergo developmentally- timed mobilization to/from the neuroblast nuclear lamina, and domain swapping a GFP reporter transgene intron with a GME relocates the transgene to the nuclear lamina in embryos. We propose that GMEs constitute a genome organizational framework and mediate gene-to-lamina mobilization during progenitor competence state transitions in vivo.

developmental biology↗

bioRxiv2024

Different folding mechanisms in prion proteins from mammals with different disease susceptibility observed at the single-molecule level

Misfolding of the protein PrP causes prion diseases in mammals. Disease susceptibility varies widely among species, despite PrP sequences differing by only a few amino acids. How these differences alter PrP folding and misfolding remains unclear. We compared the folding dynamics of single PrP molecules from three species with different disease susceptibility: dogs (immune), hamsters (susceptible), and bank voles (extremely susceptible). Measurements with optical tweezers revealed important differences between the folding cooperativity, pathways, energy barriers, and kinetics of these proteins. In contrast to the two-state folding of hamster PrP, dog PrP always folded through multiple intermediates. However, both featured rapid native folding, homogeneous energy barriers, and no readily observable misfolding. Bank vole PrP also folded via intermediates, but more slowly and via inhomogeneous barriers. Most notably, it formed several metastable misfolded states starting from the unfolded state. Analyzing the sequence of intermediates seen in pulling curves, we found significant differences in the folding pathways for dog and bank vole PrP, implying that sequence mutations altered energy barriers so as to redirect folding pathways. These results show that subtle differences in PrP sequence between species produce profound changes in folding behavior, providing insight into the factors underlying misfolding propensity.

biophysics↗

bioRxiv2023

GPX4-VIM equates a proliferating DTP state in TNBC subtypes with converged vulnerabilities to autophagy and glutathione inhibition.

Frequent metastatic relapses in Triple-Negative Breast Cancer (TNBC) patients with residual disease is a clinical challenge, largely due to tumor heterogeneity and absence of strategies that target proliferating chemo-tolerant cells. Here, we longitudinally modeled cellular state transitions from dormant drug-tolerant persister (DTP) into proliferating drug-tolerant persister (PDTP) in cells representing all TNBC subtypes. Combining subcellular imaging with phenotypic and biochemical assays, we identified distinct and converged spectrums of alterations in TNBC-PDTPs. We show that PDTPs retain acquired resistance with increased invasion potential. Moreover, Basal-Like DTPs enter into a non-reversible mesenchymal state while luminal androgen receptor-positive gain partial-Epithelial-to-Mesenchymal Transition (EMT) with vimentin upregulation. PDTP state dwells on high autophagy with reduced glutathione and GPX4 levels, rendering it vulnerable to autophagy suppression and ferroptosis. Interestingly, we find that GPX4 negatively regulates EMT and autophagy in TNBC, and an inverse correlation of GPX4-VIM expression along with autophagy genes predicts survival in TNBC patients undergoing chemotherapy.

cancer biology↗

bioRxiv2023

Anticancer, anti-inflammatory, and immune modulatory activity of ferulic acid fructo-oligosaccharide conjugated microparticle

Background and purposeFerulic acid exhibit anticancer activity but almost most of the free ferulic acid taken orally are absorbed in the stomach and extensively metabolised by the liver and hence hardly any free ferulic acid reach the large intestine to exert its beneficial activity. Fructo-oligosaccharide (dietary fibre) are resistant to gastro-intestinal enzymes and are poorly absorbed by the stomach but bioavailable in the large intestine where they are digested by gut microbiota. Ferulic acid fructo-oligosaccharide conjugate was synthesized which could self-assemble in to disc shaped amorphous microparticles, it was found to be resistant to gastro-intestinal enzymes and digestion by gut microbiota. The synthesized microparticles could be used for targeted delivery to the colon and accessed for its ability to ameliorate colo-rectal cancer and inflammation. Experimental approachThe anti-cancer activity of the FA FOS microparticle (FA FOS I) was tested in human colon cancer cell lines HT29, LoVo and compared with the toxicity to normal human colon fibroblast CCD18-Co, relative to that of conventional chemotherapeutic colon cancer drug oxaliplatin. The apoptosis induction by FA FOS I was assessed by TUNNEL (Terminal deoxynucleotidyl transferase mediated dUTP Nick-end Labelling) and FACS. The ability of the FA FOS microparticle to induce cell cycle arrest was determined. The gene expression profiling of both apoptosis related genes and cell cycle arrest related genes were analysed by using RT-PCR analysis of an array of apoptosis related genes and cell cycle related genes. In-vivo pre-clinical anti-colorectal cancer studies of FA FOS I microparticle were carried out in AOM-DSS mediated colitis associated colon cancer mice model (AOM DSS CAC) to determine its anti-cancer efficacy in the physiological, immunological and innate host microbiota setting. Key resultsThe in-vitro studies in colon cancer and normal colon cells exhibited selective cytotoxicity and apoptosis induction in colon cancer cells. The microparticle arrested the cell cycle in the G0-G1 phase. There was a reduction in 60.83% of tumour lesions in FA FOS I treated group compared to control group. The H&E histochemistry of the colon tissue revealed that there was 48.27% reduction in the malignant cell or tumour cells in the colon tissue on treatment with FA FOS I. The FA FOS conjugate treatment enhanced the gut barrier function and tight junction with the intestinal barrier guarded by the mucosal lining. The immunohistochemistry (IHC) and the immunofluorescence of the mouse colon tissue revealed the suppression of inflammation and related inflammatory cytokines in the colon. The inhibition of cell proliferation, up-regulation of tumour suppressor protein and apoptosis of the malignant or tumour cells were detected and quantified by IHC and TUNEL staining. The evaluation of immune status of the AOM DSS CAC mouse treated with FA FOS I microparticle was determined using haematological analysis of the blood lymphocytes which revealed a 9% increase in WBC count and the multiplex immunofluorescence of the colon tissue revealed an increase in the infiltration of T-helper cells and cytotoxic T-cells into the tumour microenvironment followed by the cells of the innate immune system. There was a considerable decrease in the expression of tumour suppressing PD-L1 by the tumour cells on four weeks treatment with FA FOS I microparticle. Conclusion and implicationsAll these data implicate better efficacy of the FA FOS I microparticle delivery to colon and amelioration of colo-rectal cancer, inflammation, and positive immune modulation of tumour microenvironment against tumour proliferation.

cancer biology↗

bioRxiv2023

p53 translational isoform {triangleup}40p53 orchestrates cellular SGSH levels via microRNA-4671-5p to modulate cell cycle

{Delta}40p53, the only translational isoform of p53, modulates the full-length p53 (FLp53) activity and independently regulates targets such as the miR-186-5p-YY1 axis. To identify additional miRNAs regulated by {Delta}40p53, we performed small RNA sequencing. We found that overexpression of {Delta}40p53, but not FLp53, significantly downregulated miR-4671-5p. Expression of both isoforms at varying ratios revealed that miR-4671-5p may be modulated by FLp53 in a {Delta}40p53-dependent manner. In silico analysis identified SGSH (N-sulfoglucosamine sulfohydrolase) as a potential miR-4671-5p target. SGSH expression showed inverse correlation with miR-4671-5p in cancer datasets and prognostic significance. SGSH mRNA and protein levels were reduced upon miR-4671-5p overexpression or si{Delta}40p53 treatment, confirming regulatory linkage. Functionally, miR-4671-5p overexpression induced intra-S-phase cell cycle arrest, implicating SGSH in cell cycle regulation. These results reveal a novel {Delta}40p53-miR-4671-5p-SGSH axis that impacts cell cycle progression and may contribute to cancer outcomes. Our findings highlight the distinct regulatory role of {Delta}40p53, independent of FLp53, in maintaining cellular and metabolic homeostasis via miRNA-mediated mechanisms.

molecular biology↗

bioRxiv2022

Water-Quality analysis and Fish diversity of Southern West Part of the West-Bengal

Marine fishes are one of the important factors to stabilize the local aquatic ecosystem and regulating socio-economy of local fishermen. In this study we emphasized upon finding out the interrelationship in the water quality, anthropogenic activity, and fish habitat through the 31km stretch of East Medinipur coast in West Bengal, India which is known for its tourist destinations. The study was conducted monthly on different trawler fish landing sites from Dec 2018 to Dec 2021. During this period, we took fish samples and identified them. We took water quality data such as SST, Concentration of Chl-a, Turbidity, and DO for further correlation between the water quality and species diversity. Total 154 numbers of commercially important marine fish species were documented. Among them, 12 species are from Elasmobranch and the rest is Actinopterygii. As per the IUCN database, 13% of the total fish species are under the red list category and 16% of the species showing decreasing population trend. After analyzing the water quality data, we found out that DO, SST, Turbidity, and Chlorophyll-A correlate with the species richness and it also differs during the seasons.

ecology↗

bioRxiv2020

Recapitulating the frataxin activation mechanism in an engineered bacterial cysteine desulfurase supports the architectural switch model

Iron-sulfur (Fe-S) clusters have a key role in many biochemical processes and are essential for most life forms. Despite recent mechanistic advances in understanding the Fe-S cluster biosynthetic pathway, critical questions remain unresolved. Although human NFS1 and E. coli IscS share [~]60% sequence identity, NFS1 exhibits low activity and requires activation by the Friedreichs ataxia protein frataxin (FXN) for in vivo function. Surprisingly, structures of the human complex reveal three distinct quaternary structures with one form exhibiting the same subunit interactions as IscS. An architectural switch model has been proposed in which evolutionarily lost interactions between NFS1 subunits results in the formation of low-activity architectures; FXN binding compensates for these lost interactions and facilitates a subunit rearrangement to activate the complex. Here, we used a structure and evolution-guided approach to identify three conserved residues proposed to weaken interactions between NFS1 subunits and transplanted these amino acids into IscS. Compared to native IscS, the engineered variant had a 4000-fold weaker dimer interface and diminished activity that correlated with the absence of the second catalytic subunit. Remarkably, the addition of the FXN homolog to the engineered variant stimulated the decay of the Cys-quinonoid pyridoxal 5-phosphate intermediate, shifted IscS from the monomeric to dimeric form, and increased the cysteine desulfurase activity, reproducing results from the human system and supporting the architectural switch model. Overall, these studies indicate a weakening of the homodimeric interface was a key development during the evolution of the eukaryotic system and provide new insights into the role of FXN.

biochemistry↗

bioRxiv2018

Short-term aerobic training does not improve memory functioning in relapsing remitting multiple sclerosis - a randomized controlled trial

BackgroundOnly few aerobic exercise intervention trials specifically targeting cognitive functioning have been performed in MS.\n\nObjective and methodsThis randomized controlled trial aimed to determine the effects of aerobic exercise on cognition in relapsing-remitting MS. The primary outcome was verbal memory (Verbal learning and memory test, VLMT). Patients were randomized to an intervention group (IG) program or a waitlist control group (CG). Patients in the IG exercised according to an individually tailored training schedule (with 2-3 sessions per week for 12 weeks). The primary analysis was carried out using the intention-to-treat (ITT) sample with ANCOVA adjusting for baseline scores.\n\nResults77 RRMS patients were screened and 68 participants randomized (CG n=34; IG n=34). The sample comprised 68% females, had a mean age of 39 years, a mean disease duration of 6.3 years, and a mean EDSS of 1.8. No significant effects were detected in the ITT analysis for the primary endpoint VLMT or any other cognitive measures. Moreover, no significant treatment effects were observed for quality of life, fatigue, or depressive symptoms.\n\nConclusionThis study failed to demonstrate beneficial effects of aerobic exercise on cognition in RRMS.\n\nThe trial was prospectively registered at clinicaltrials.gov (NCT02005237).

clinical trials↗

bioRxiv2018

Discovery of Large Disjoint Motif in Biological Network using Dynamic Expansion Tree

Network motifs play an important role in structural analysis of biological networks. Identification of such network motifs leads to many important applications, such as: understanding the modularity and the large-scale structure of biological networks, classification of networks into super-families etc. However, identification of network motifs is challenging as it involved graph isomorphism which is computationally hard problem. Though this problem has been studied extensively in the literature using different computational approaches, we are far from encouraging results. Motivated by the challenges involved in this field we have proposed an efficient and scalable Motif discovery algorithm using a Dynamic Expansion Tree (MDET). In this algorithm embeddings corresponding to child node of expansion tree are obtained from the embeddings of parent node, either by adding a vertex with time complexity O(n) or by adding an edge with time complexity O(1) without involving any isomorphic check. The growth of Dynamic Expansion Tree (DET) depends on availability of patterns in the target network. DET reduces space complexity significantly and the memory limitation of static expansion tree can overcome. The proposed algorithm has been tested on Protein Protein Interaction (PPI) network obtained from MINT database. It is able to identify large motifs faster than most of the existing motif discovery algorithms.

bioinformatics↗